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How are brain and spinal cord tumors diagnosed in children?

Brain and spinal cord tumors are usually found because of signs or symptoms a child is having. If a tumor is suspected, tests will be needed to confirm the diagnosis.

Medical history and physical exam

If your child has symptoms that suggest a brain or spinal cord tumor, the doctor will get a complete medical history, focusing on the symptoms and when they began. The doctor will also do a neurologic exam to check your child’s brain and spinal cord function, if possible. Depending on the child’s age, the exam may test reflexes, sensation, muscle strength, vision, eye and mouth movement, coordination, balance, alertness, and other functions.

If the results are abnormal, your child’s doctor may refer you to a neurologist (a doctor specializing in medical treatment of nervous system diseases) or a neurosurgeon (a surgeon specializing in nervous system diseases), who will do a more detailed exam and might order other tests.

Imaging tests

Your child’s doctors may order one or more imaging tests. These tests use x-rays, strong magnets, or radioactive substances to create pictures of internal organs such as the brain and spinal cord. The pictures may be looked at by doctors specializing in this field (neurosurgeons, neurologists, and neuroradiologists) as well as by your child’s primary care doctor.

Magnetic resonance imaging (MRI) and computed tomography (CT) scans are used most often for brain diseases. These scans will show a brain or spinal cord tumor, if one is present, in almost all cases. Doctors can often also get an idea about what type of tumor it might be, based on how it looks on the scan and where it is in the brain (or spinal cord).

Magnetic resonance imaging (MRI) scan

MRIscans are very good for looking at the brain and spinal cord and are considered the best way to look for tumors in these areas. MRI images are usually more detailed than those from CT scans (described below). But they do not image the bones of the skull as well as CT scans and therefore might not show the effects of tumors on the skull.

MRI scans create detailed images using radio waves and strong magnets instead of x-rays, so they do not expose the child to radiation. A contrast material called gadolinium may be injected into a vein before the scan to help see details better.

MRI scans can take a long time – often up to an hour. Your child may have to lie on a table that slides inside a narrow tube, which is confining and can be distressing. The test also requires a person to stay still for several minutes at a time. Some children might need medicine to help them relax or even be asleep during the test. Open MRI machines may be another option, though they might result in less detailed images. The MRI machine makes loud buzzing and clicking noises that your child may find disturbing. Some places provide headphones or earplugs to help block this noise out.

Magnetic resonance angiography (MRA): This special form of MRI may be done to look at the blood vessels in the brain. This can be very useful before surgery to help the surgeon plan an operation.

Magnetic resonance spectroscopy (MRS): This test is like an MRI, except it measures the radio wave interactions with different chemicals in the brain. MRS highlights some features of brain tumors that may not be seen clearly with MRI. It creates graph-like results called spectra (but crude images can also be created). This might give clues to the type of tumor, but in most cases a biopsy of the tumor is still needed to get an accurate diagnosis. MRS can also be used after treatment to help determine if an area that still looks abnormal on another test is remaining tumor or if it is more likely to be scar tissue.

Magnetic resonance perfusion: For this test, also known as perfusion MRI, a contrast dye is injected quickly into a vein. A special type of MR image is then obtained to look at the amount of blood going through different parts of the brain and tumor. Tumors often have a bigger blood supply than normal areas of the brain. A faster growing tumor may need more blood.

Perfusion MRI can give doctors an idea of the best place to take a biopsy. It can also be used after treatment to help determine if an area that still looks abnormal is remaining tumor or if it is more likely to be scar tissue.

Functional MRI (fMRI): This newer type of MRI looks for tiny blood flow changes in an active part of the brain. It can be used to determine what part of the brain handles a function such as speech, thought, sensation, or movement. Doctors can use this to determine which parts of the brain to avoid when planning surgery or radiation therapy.

This test is similar to a standard MRI, except that your child will be asked to perform specific tasks (such as answering simple questions or moving their fingers) while the scans are being done.

Computed tomography (CT) scan

The CT scan uses x-rays to produce detailed cross-sectional images of your child’s brain and spinal cord. Instead of taking one picture, like a regular x-ray, a CT scanner takes many pictures as it rotates around your child while he or she lies on a table. A computer then combines these pictures into images of slices of the body. Unlike a regular x-ray, a CT scan creates detailed images of the soft tissues in the body.

For brain and spinal cord tumors, CTscans are not used as often as MRI scans, which give slightly more detailed images and do not use radiation. Still, there are instances where CT scans may have advantages over MRI scans:

CT scans take much less time than MRIs, which can be particularly helpful for children who have trouble staying still.

CT scans provide greater detail of the bone structures near the tumor than MRIs do.

CT angiography (CTA), which is described below, can provide better details of the blood vessels in and around a tumor than MRA in some cases.

Before the scan, your child may get an injection of a contrast dye through an IV (intravenous) line. This helps better outline any tumors that are present. The contrast contains iodine and may cause some flushing (a feeling of warmth, especially in the face). Some people are allergic to the dye and get hives. Rarely, more serious reactions like trouble breathing or low blood pressure can occur. Be sure to tell the doctor if your child has any allergies or has ever had a reaction to any contrast material used for an imaging test.

CT scans take longer than regular x-rays but not as long as MRI scans. Your child will need to lie still on a table while they are being done. A CT scanner has been described as a large donut, with a narrow table that slides in and out of the middle opening. Some people feel a bit confined by the ring they lie in while the pictures are being taken, although it is not as narrow as an MRI tube. Some children may need to be sedated before the test to keep them as still as possible and help make sure the pictures come out well.

CT angiography (CTA): For this test, your child gets an injection of contrast material through an IV line while he or she is in the CT scanner. The scan creates detailed images of the blood vessels in the brain, which can help doctors plan surgery. CT angiography can provide better details of the blood vessels in and around a tumor than MR angiography in some cases.

Positron emission tomography (PET) scan

For this test, a radioactive substance (usually a type of sugar known as FDG) is injected into the blood. The amount of radioactivity used is very low and passes out of the body within a day or so. Because tumor cells in the body are growing quickly, they absorb larger amounts of the sugar than most other cells. After about an hour, your child is moved onto a table in the PET scanner. He or she will lie on the table for about 30 minutes while a special camera creates a picture of areas of radioactivity in the body. If your child is not able to stay still for the test, this might require sedation.

The PET scan image is not as detailed as a CT or MRI scan, but it can provide helpful information about whether abnormal areas seen on other tests (such as MRIs) are likely to be tumors or not.

This test is also useful after treatment to help determine if an area that still looks abnormal on an MRI scan is remaining tumor or if it is more likely to be scar tissue. Any remaining tumor will show up on the PET scan, while scar tissue will not.

Angiogram

For this test, a special dye is injected into blood vessels near the tumor, and then the area is viewed with x-rays. This helps doctors look at a tumor’s blood supply. This test is not done much for brain or spinal cord tumors anymore, as it has largely been replaced by magnetic resonance angiography (MRA) or computerized tomographic angiography (CTA).

Brain or spinal cord tumor biopsy

Imaging tests such as MRI and CT scans may show that a child has a brain or spinal cord tumor. But usually the type of tumor can be determined only by removing a sample of it, which is called a biopsy. A biopsy may be done as a procedure on its own for diagnosis, or it may be part of surgery to treat the tumor.

The biopsy samples are looked at under a microscope by a pathologist (a doctor specializing in diagnosis of diseases by lab tests). Sometimes it might need to be looked at by a neuropathologist, a pathologist who specializes in nervous system diseases. The pathologist determines if the tumor is benign or malignant (cancerous) and exactly what type of tumor it is.

In some cases (such as for many astrocytomas or brain stem gliomas), it may not be necessary or possible to biopsy the tumor safely, so the diagnosis is made based only on how the tumor looks on imaging tests.

Biopsies can be done in different ways.

Stereotactic needle biopsy

This type of biopsy may be used if imaging tests show surgery to remove the tumor might be too risky (such as with some tumors in vital areas or deep within the brain) but a sample is still needed to make a diagnosis.

Depending on the situation, the biopsy may be done with the child awake or under general anesthesia (asleep). If the child is awake, the neurosurgeon injects a local anesthetic into areas of skin over the skull to numb them. (The skull and brain itself do not feel pain.)

A rigid frame may then be attached onto the child’s head. This helps make sure the surgeon will target the tumor precisely. A small cut is made in the scalp, and a small hole is drilled in the skull. An MRI or CT scan is used along with the frame to help the neurosurgeon guide a hollow needle into the tumor to remove small pieces of tissue.

Another approach is to get an MRI or CT scan, use scalp markers or facial and scalp contours to create a map of the inside of the head, and then use an image-guidance system to direct the needle into the tumor. This still requires making an incision and drilling a small hole into the skull.

The biopsy samples are then looked at under a microscope by a pathologist. The doctor can usually tell exactly what type of tumor it is. This helps determine the best course of treatment and the prognosis (outlook).

Craniotomy

If imaging tests show the tumor can be treated with surgery, the neurosurgeon may not do a needle biopsy. Instead, he or she may do an operation called a craniotomy (described in the “Surgery” section) to remove all or most of the tumor. (Removing most of the tumor is known as debulking.)

Small samples of the tumor are looked at right away by the pathologist while the child is still in the operating room, to get a preliminary diagnosis. This can help guide treatment, including whether further surgery should be done at that time. A final diagnosis is made a within a few days in most cases.

Lumbar puncture (spinal tap)

This test is used to look for cancer cells or chemicals released by tumors in the cerebrospinal fluid (CSF), which is the liquid that bathes the brain and spinal cord. For this test, the doctor first numbs an area in the lower part of the back over the spine. The doctor may also recommend that the child be given something to make them sleep so the lumbar puncture can be done more easily and safely. A small, hollow needle is then placed between the bones of the spine to withdraw some of the fluid.

The fluid is looked at under a microscope for cancer cells. The CSF can also be tested for certain substances released by some germ cell tumors.

Lumbar punctures are often used if a tumor has already been diagnosed as a type (such as a medulloblastoma) that can commonly spread through the CSF. Information from the spinal tap can influence treatment.

Bone marrow aspiration and biopsy

Because some tumors (especially medulloblastomas) can spread beyond the nervous system, in some instances the doctor may recommend looking at cells in your child’s bone marrow (the soft, inner part of certain bones) to see if tumor cells have spread there.

The bone marrow aspiration and biopsy are often done at the same time. The samples are usually taken from the back of the pelvic (hip) bone, but in some cases they may be taken from other bones.

In bone marrow aspiration, the skin over the hip and the surface of the bone is cleaned and then numbed with local anesthetic. In most cases, the child is also given other medicines to make them drowsy or even asleep during the procedure. A thin, hollow needle is then inserted into the bone, and a syringe is used to suck out (aspirate) a small amount of liquid bone marrow.

A bone marrow biopsy is usually done just after the aspiration. A small piece of bone and marrow is removed with a slightly larger needle that is pushed down into the bone. Once the biopsy is done, pressure is applied to the site to help stop any bleeding

The specimens are then looked at under a microscope for tumor cells.

Blood and urine tests

These lab tests are rarely used to diagnose brain and spinal cord tumors, but if your child has been sick for some time they may be done to check how well the liver, kidneys, and some other organs are working. This is especially important before any planned surgery.

If your child is getting chemotherapy, blood tests will be done routinely to check blood counts and to see if the treatment is affecting other parts of the body.